KC Weed News - April 2009
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Yellow flag iris is such a successful invader that many people assume it is native to North America. In fact, some wetland plant guides have included this species without mentioning that it is from Europe, leading to even more confusion. Perhaps part of the problem is that yellow flag iris looks very much at home in our wetlands. In its native range in Europe and western Asia, this plant is found in the same kind of wet habitats as here, and can even be somewhat aggressive, but it more or less co-exists with other species in its native range. In North America, yellow flag iris has few natural checks on its growth and it more often forms large, single-species stands that exclude native plants and animals.
Yellow flag iris also has a bad habit of clogging up irrigation canals and natural streams. One study in Montana found that this plant was capable of closing in a stream by 10 inches a year due to its ability to trap sediment and quickly colonize the new ground, moving out into the creek and even closing off small waterways completely. Seeds clog up irrigation screens and pipes and the thick growth slows down flow and blocks access to streams. If that wasn’t bad enough, yellow flag iris is also toxic and can make livestock and wildlife sick if they eat too much of it. Birds don’t even eat the seeds. In fact, our native wildlife do not seem to make use of this plant at all, and it makes life pretty tough for them by crowding out the plants they do use and blocking access to waterways.
No iris enthusiasts I’ve spoken with would plant yellow flag iris anymore, but it has been very popular in the past as a garden plant and continues to be sold and planted. In fact, it is thought that yellow flag first made its way into natural waterways when low-lying gardens were flooded and rhizome fragments got washed away and deposited in new locations. Now that yellow flag is established in so many natural waterways, it is spreading through natural disturbances and seed dispersal as well as escaping from gardens. There are attractive, non-invasive alternatives to yellow flag iris in the Garden Wise booklet, so hopefully people can avoid planting any more of this problem plant. Dealing with the naturalized populations is much more difficult.
If you have ever tried to get rid of yellow flag iris, I certainly don’t have to tell you how well this plant thrives in our region or how incredibly tough and resilient it is. In a garden, as with controlling any iris, you need to thoroughly remove all of the rhizome and root matter. Rhizomes can survive being dried out for considerable time and will certainly survive in most home compost piles, so disposal in the garbage or with the city yard waste is probably best. In a natural area or along water, it is even more important to carefully remove every root and rhizome, since the water will help move any remaining rhizome bits to a new, more hospitable location. Although rhizomes are the easiest way for this plant to re-sprout or move to a new area, yellow flag also produces abundant, viable seeds that help it spread as well. What’s worse, the seeds are buoyant (they contain gas inside a hard outer coat) and they can stay afloat for up to seven months as they drift on to new shores. Because it takes a few years for yellow flag to mature, removing flowers and seed pods can greatly reduce the spread of this plant and buy you time to remove the mature plants. Shade will also reduce seed germination, so covering or mulching where plants have been removed will help a lot in reducing new growth. Chemical control works as well, although this is often limited by the proximity to water and the need for special permits and licenses. For more information on chemical control, you can contact our office or read our Best Management Practices for yellow flag iris (follow the link at the bottom of the yellow flag iris page).
Although I would love to recommend that all yellow flag iris in King County be removed, this is not realistic. However, when it is possible to do so and especially as a part of a shoreline or wetland restoration project, it would be very beneficial to remove it. Yellow flag iris is well on its way to becoming irreversibly entrenched in our county’s waterways, making it even more important to keep it at bay where it is still manageable or not yet established. If you would like more information on this plant, or other noxious weeds, please do not hesitate to contact us at 206-296-0290 or noxious.weeds@kingcounty.gov or visit our website at www.kingcounty.gov/weeds.
Weed Tips for April
Celebrate Earth Day by pulling English ivy. Nothing says Earth Day in the Pacific Northwest like tackling ivy. Just be careful around storm-damaged trees – never pull ivy down from the upper parts of a tree since this might injure the tree and will most certainly injure you if branches fall off. Just pry the vines off the bark of the tree up to where you can comfortably reach and all the way down to the ground. Ivy on the ground can be pulled up with a generous helping of elbow grease, a well-placed shovel, and clippers to cut off roots you can’t dig up.
The cold, wet spring has delayed some weeds, but others are already bursting with growth. Weeds are good survivors and our cold, wet winter and spring will be no problem for most of them. Expect to have a slower start for many weeds and don’t be fooled if it looks better than you expected in some places. The weeds are probably still there, just slower to emerge. On the other hand, many weeds have not been slowed down at all and it will be a challenge to get out to them quickly enough, especially now that we’ve finally had some warm weather. Remember that weeds are those plants that can survive better, grow faster and spread better than other plants. In fact, the tough winter will probably make some weed problems worse where tender ornamentals or even native plants were harmed by the cold and wet this year and weeds will quickly move in to the new territory if we are not quick to stop them.
April is a great time to mulch planting beds. Mulch inhibits weed growth and retains soil moisture. A couple of inches of fresh arborist chips (chipped up tree trimmings) or bark will save you hours of weeding this summer. Avoid piling on too much mulch around trees (10 inches or more is too much) and keep the mulch a few inches away from tree trunks. Too much mulch can act as a barrier—it repels water and deprives the tree of oxygen. Using compost as mulch is great for improving the soil and water retention, but won’t stop weeds, so it is good to add chips or bark on top of compost if you want to avoid pulling weeds.
Consider waiting awhile before cutting blackberry brambles if you can only do it once or twice this year. Of course it is best to keep blackberries cut back as much as possible if you are trying to starve their roots. However, time and resources are limited for most of us and you may not be able to get out there every week or so (which is what would be needed this time of year). If you can only cut your blackberries back once or twice this year, then wait until they have depleted some of their root reserves, so they don’t just grow right back again. If you can only cut them once a year, the best time to do so is actually when they are flowering. That is the time they have the least energy reserves and when cutting will do the most damage. However, if your plan is to cut them down and then dig up the roots, then by all means do it now! In fact, spring is a great time for that method, since the soil is moist and the brambles are easier to see before they leaf out fully.
We are taking registrations for our annual noxious weed workshops for vegetation management crews and others who need to identify and manage noxious weeds. Session dates are May 6 and May 13. Topics this year include updates and refreshers on identifying and controlling priority noxious weeds, a presentation by Jeff Britt from WSDA on the “Keys to Legal Pesticide Applications and Record Keeping”, updates on using biocontrol in the county, and a special training session on using stem-injection guns to control knotweed. Participants in the stem-injection training can apply to borrow stem-injectors from the noxious weed program for controlling knotweed in their own projects. (By the way, for those of you just interested in knotweed stem-injection training, we will also be offering evening knotweed control workshops in June and July for county residents).The full agenda is on our workshops page. Both classes are free and open to the public but space is limited. WSDA pesticide license recertification credits have been requested for these classes (4 credits requested). Register at 206-263-6468 or sasha.shaw@kingcounty.gov. Please provide the name(s), agency or company, phone number and email. Learn about Washington’s Native Plants This Spring The Washington Native Plant Society is now seeking applications for the Native Plant Stewardship Program in East King County. Participating cities in King County include Bellevue, Issaquah, Kirkland, and Sammamish. The 10-week training is held on Fridays from April 24 through June 26, 2009, in Bellevue. This training is taught by top professionals on various topics such as native plants, habitat restoration, invasive weeds, northwest ecology, and working with volunteers. In exchange for this free training, stewards will commit to 100 hours of volunteer service implementing the skills learned in these classes. Native Plant Steward teams will be formed to work on habitat restoration projects in each of the partner communities: Kirkland, Issaquah, Bellevue, Sammamish and east King County. For more information regarding the Native Plant Stewardship Program and to download the application form: http://www.wnps.org/npsp/king/program.html. Application deadline is April 15, 2009. For questions about the Native Plant Stewardship Program please contact Dangelei Fox at npsp@wnps.org or call (206) 660-3968. The Native Plant Stewardship Program is an education project of the Washington Native Plant Society's Central Puget Sound Chapter and is made possible by funding from the cities of: Bellevue, Issaquah, Kirkland (through a King Conservation District Grant), Sammamish, and additional funding support provided by a King County Department of Natural Resources and Parks Waterworks grant. Please pass along this information to others on the greater Eastside who might be interested.
Help Save A Forest: Volunteer for Bridle Trails State Park Restoration The 480-acre Bridle Trails State Park, located where Redmond, Kirkland and Bellevue meet, is an excellent example of the kind of lowland conifer forest that used to cover most of King County. In addition to its many riding trails and arenas, the park supports a thriving forest with relatively few invasives, many healthy, mature conifers, and lots of young conifer regeneration in the understory. However, a number of troublesome garden escapees and other non-natives are invading, including English ivy, cherry laurel, English holly, and, of course, Himalayan blackberry. Since 2005, the Bridle Trails Park Foundation and park ranger have been organizing volunteers to attack the invasives as part of a new park stewardship program. This year’s Earth Day event will be the fifth, and the group has also had several smaller work parties each year. A total of about 350 volunteers have pitched in so far, and volunteers continue to be critical to the success of the project, especially with this year’s state budget crisis. The goal is to reduce the invasive plants to levels that have minimal ecological impact. Many hundreds of plants have been removed, but some areas are coming back. This will be a long-term effort that will also include planting native plants in some areas. Along with the stewardship program, the Foundation also sponsors nature walks for the general public focusing on plants, fungi, and birds in the park, as well as forest ecology. The Foundation and Park Ranger have also worked with three local schools, leading field trips into the park and providing classroom support. The group is also working on an interpretive trail focused on forest biodiversity. For more information please see the Foundation’s website at www.bridletrails.org or contact Jim Erckmann at erckmann1@verizon.net. You can help protect this great park by attending the upcoming work party: Saturday, April 18, 9 a.m. till noon, Bridle Trails State Park
Please join other volunteers and help control non-native, invasive plants in Bridle Trials State Park. Meet in the picnic area north of the entrance on 116th Ave. NE at NE 53rd St. Bring gloves and hand pruners, and wear sturdy clothes. Refreshments and lunch provided. Info at www.bridletrails.org.
Pull Weeds for Earth Day It’s been a long, cold winter and I think a great way to get over the winter blues and to celebrate spring is to help out at a local park or natural area. Earth Day is on a Wednesday this year – April 22 – so look for work parties especially on April 18 and April 25, but also scattered throughout the month. On the eastside, check out the Earth Day Event in Bridle Trails State Park, Saturday, April 18, 9-12 (see above for details). In Kirkland, volunteer on April 25 at Juanita Bay Park from 9-12 (see the Green Kirkland calendar for more events). In Sammamish, choose to volunteer either at Pine Lake Park or at Illahee Trail (a.k.a. Llama Landing or Grassis Lake). Both events are 9-12. See the Sammamish website for more information. King County Parks restoration projects can also use your help. On April 18, help out at Cavanaugh Pond and on April 25 you can choose between Chinook Bend on the Snoqualmie River and Red Town Meadow on Cougar Mountain. More details and contact information can be found on the county stewardship volunteer events web page (a.k.a. The Dirt). For a great Earth Day event in Seattle with both fun and work, check out Earth Day with Duwamish Alive! on April 18 sponsored by People for Puget Sound (and lots of other organizations and agencies). The City of Seattle has declared the whole month of April as Earth Month so check out Seattle’s Work Party Calendar for lots of great activities all month long and beyond. For volunteer events all along the Mountains to Sound Greenway, check out the Greenway Trust Volunteer Events Calendar. Two more great resources for volunteer events are EarthCorps’ Volunteer Calendar and Cascade Land Conservancy’s Events Calendar. For volunteering in your city, contact your local parks department for work parties – there’s always lots to do this time of year! And if I left your events off, I apologize. Just drop me an email next year around March and I’ll get it in next time. Happy volunteering everyone!
Come Visit the Noxious Weed Booth
April 18, Shoreline Natural Yard Care Fair, Central Market, Shoreline, 155th & Aurora, 9-3 April 22, King County Earth Day Expo, Westlake Center, Seattle, 10-2
Tips for Reducing Weeds in your Compost I came across a very useful article on avoiding weed problems in your backyard compost. Although it’s best to avoid putting weed seeds into your own compost piles whenever possible, sometimes it’s unavoidable or preferable to other options. According to a press release from the Weed Science Society of America, the keys to maximum weed seed death in compost are time, temperature and turning. It takes 30 days of exposure to temperatures of 145 degrees or more to destroy many tough weed seeds. If your compost feels “uncomfortably hot” when you reach in, then you’ve probably got it hot enough. Turning and mixing are also key because that’s how you expose all the weed seeds to that hot temperature. Of course, as they point out, if you put compost onto areas with existing weeds, they will benefit from it as much as the plants you want to grow. So, make sure to manage your weeds as well as your compost. And please don’t put seeds of regulated noxious weeds into your compost – the risk of even a few seeds surviving is just too high. The press release also has more great tips on making great compost and reducing weed problems.
British Columbia Funds Coordinated Invasive Weed Control In today’s world of budget cuts and worries about funding government projects, it’s nice to see some funding being dedicated to invasive and noxious weed control across the border. British Columbia shares many of the same invasive weeds as us and any work done up north benefits us as well. In addition to weeds crossing borders on vehicles, water, wind and so forth, there are many ornamentals brought in from British Columbia that could carry noxious weed seeds or even be noxious weeds themselves. So, hats off to them for working on a coordinated plan of attack to reduce impacts of invasive weeds and for dedicating some funding to make it work. Read more details in the recent news story on this from Alberta Farmer’s online journal: http://www.albertafarmexpress.ca/issues/ISArticle.asp?id=98503&PC=FBC&issue=04072009.
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